Mailing List flyrotary@lancaironline.net Message #8547
From: DaveLeonard <daveleonard@cox.net>
Subject: RE: [FlyRotary] Re: water temp sender
Date: Sun, 23 May 2004 19:24:04 -0700
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Message
I would ditto what Rusty said but if you study the cooling passages well you will note that the second pass is the hot part of the engine.  In other words, the coolant comes the engine.  goes along the top and spark plug side, past your sensor, then down and across the combustion chambers and exhaust/intake side, then back out at the pump.  This further explains the difference in temp.
 
Dave Leonard
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]On Behalf Of Russell Duffy
Sent: Sunday, May 23, 2004 8:24 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: water temp sender

I now have another question.  Since I found out that I'm measuring water temperature twice, and not measuring oil temperature at all, now I have another issue. I getting about a 20 degree difference between the two coolant temps.

The way you measured the temps is the way it should be, as long as the water is flowing well.  The water leaves the engine at the thermostat housing, so it has picked up all the heat it can from the engine.  That will be the hottest point.  The water then goes to the radiators, cools off, and comes back to the engine.  It then goes through about half the engine to get to the point where the other sensor is located.  It should be cooler here, than it will be when it makes it through the other half of the engine to get to the thermostat housing.  Ed must have a wacky gauge :-)

For water, the standard is to measure it as it leaves the engine, which is the hottest point.  I would think that's what you'd want to do with the oil as well, but unfortunately, there's no practical way to do that.  The oil drips back to the pan from different places, and you can't measure that return flow directly.  You can measure the pan temp, as I did originally, but it's not the best reading, since there isn't really a constant flow of oil past the sensor.   I suspect that measuring the oil as it returns to the engine was selected as the next logical point.  I have the pan temp hooked up as an Aux temp on the EM-2, but I can't say I've looked at it yet.  Maybe when Tracy gets around to that data logging... :-)

Cheers,
Rusty (better to be covered in aluminum than fiberglass)  
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